1.0 Field of the Invention
A method and an apparatus for detecting and locating explosive, biological, chemical, and radioactive devices in ducts, piping, or other fluid flow systems in or on the exterior of various structures such as buildings, transportation systems (airplanes, ships, trains, buses, etc.), and various types of infrastructure (containers, packages, luggage, fluid flow systems, ducts, pipes, conduits, dams, bridges, tunnels, etc.) is described. The method and apparatus can also be used to detect and locate these dangerous or hazardous materials in the rooms, compartments, enclosures, containers, or difficult to access areas in these buildings, transportation systems, and infrastructure, either through the ductwork or by access into that portion of the structure (e.g., room) to be searched. The method can also be used to quantify the magnitude of the threat. This method and apparatus can also be used to detect, locate, and/or quantify the levels of naturally occurring biological and chemical hazards, such as mold and bacteria, which may develop in the ductwork, walls, or other parts of these structures. This detection, location, and quantification method uses a conservative and one or more interactive tracers that are injected into the duct at one location and then monitored at the same or another location in the duct. This method can also be used in a non-fluid flow system, such as a room, by injecting the tracers into the room or a specific area in a structure and then withdrawing the tracers through the injection point or another point in the room, the duct system, or another room in the structure. The ductwork can also be used as a communication network to detect the presence of a biological, chemical or explosive threat in a room or area or all rooms or areas within a building or structure without physically accessing that room or area. This invention is related to the invention disclosed in U.S. patent application Ser. No. 10,960,407, filed Oct. 6, 2004, titled Method and Apparatus for Locating Leak Holes in a Pipeline Using Tracers.
In the preferred embodiment, the tracers are introduced into the room or the area to be interrogated through the inlet vent of the inlet duct and then are returned to the return duct through the return vent. Provided the tracer injection and tracer measurement systems are appropriately located (e.g., the building's HVAC unit), all rooms and all of the ductwork can be interrogated. For most threat applications, both detection and location are required. For some applications, like the detection of dangerous or hazardous materials such as explosives, biological and chemical agents in the ductwork or in a room, quantification may not be essential once the threat is detected and located, because these threats must be removed regardless of their magnitude. For other applications, like the detection of mold and bacteria in the ductwork, quantification is important, because the quantity of mold or bacteria detected in the ductwork may not be sufficient to warrant the removal until it reaches a critical level. Detection, location, and quantification are accomplished by analysis of the characteristic features of the measured curves of tracer concentration obtained with a gas chromatograph (GC) or a sensor system that senses or measures the magnitude of the specific substances of interest. Various types of interactive tracers may be used, including partitioning and reactive gaseous tracers.
This method and apparatus has many different types of applications in many different types of structures. The specific application will depend on the threat and whether a targeted measurement is being made or a monitoring system is being used. The method will also depend on what type of information (detection, location, or quantification) is required. The method will also depend on whether the threat is believed to be in the ductwork, in the rooms or areas accessible through the ductwork, or in rooms or areas regardless of access through flow channels such as the ductwork.
A slug of the tracers, which may include both conservative and interactive tracers, can be introduced into the ductwork or areas to be searched or monitored, transported through the ductwork or areas to be searched or monitored with an inert gas, and then measured at another location in the ductwork or structure. Instead of a slug of tracers, the entire ductwork or areas to be searched or monitored could be filled first with the interactive tracers and then measured at the same or another location in the ductwork or areas by use of an inert gas to transport the tracers to the measurement point or by withdrawing the tracers under a vacuum. The ductwork or other piping (e.g., electrical conduit) that may access one or more rooms in the building or one or more areas within the various building, transportation, or structures can be used to introduce the tracers into the rooms or areas to be searched or monitored and then measured by producing a flow stream that pulls the tracers back out of the rooms or areas or is sensed at a point that specifically accesses each room or area.
Various types of interactive tracers may be used, including partitioning and reactive tracer gases. The tracers are selected specifically to detect and/or locate, and/or measure the concentration of the specific hazardous materials or devices of interest. Different tracers are usually required to detect explosives, biohazards, or dangerous chemicals or gases. There may be more than one tracer and/or type (e.g., reactive or partitioning) of tracer to use for each type of threat target. The tracer that might be used to detect the explosive TNT may not necessarily be the one used to detect the explosive C4. If detection is the primary objective, then a tracer that interacts with the threat substance the quickest would be the best choice. Both reactive and partitioning tracers will suffice. If the threat target material also needs to be located, then a partitioning tracer would be the preferred choice, because the structure being interrogated can be rapidly flushed once the tracer has had time to partition into the hazardous material and the arrival time of the tracer partitioning back into the flow stream can be measured. This measurement will take more time and needs better fluid flow controls than the detection measurement. Quantification can be accomplished with both reactive and partitioning tracers.
1.2 Brief Discussion of Prior Art
At the present time, the methods used to detect dangerous or hazardous substances such as explosives, biological, or chemical agents require a personal, mechanical, or robotic search of the ductwork, the piping system, or each room or area where the explosives may be hidden. An individual or a team of individuals must visually access and search each area where dangerous or hazardous substances are suspected. In a building, this may require a room-by-room search. It may require a person crawling through the ductwork, or by placing a robotic crawler with a camera or chemical sensing device attached in the ductwork. Dogs, which are very adept at detecting the presence of explosives, for example, are often used. Dogs are very effective and can increase the speed and safety of a search operation. Various explosive sensing and measurement devices may also be used to detect the presence of explosives from the chemical or physical properties of the explosives. These sensing devices must also be brought to each area to be searched and are generally carried by the individuals of the search team. However, they can be attached to a robotic system for safety (e.g., in a room search) or when the search area cannot be accessed by an individual or a dog (e.g., small ducts, sewer pipe).
The current approach to detection is very labor intensive and very slow; thus, it is very expensive. Since it can be slow and tedious, the presence of dangerous or hazardous substances can also be missed by the individuals as they tire or get careless. More importantly, this approach also requires the a priori knowledge that dangerous or hazardous substances might be present in the building, transportation system, or infrastructure so that a search can be initiated.
A remote sensing system is needed that can check an entire building, transportation system, or structure without an individual or animal physically accessing the area to be search. This remote sensing system can be used when dangerous or hazardous substances are suspected, or more importantly, it can be used as a remote monitoring system to routinely check a building, transportation system or structure in which a biological, chemical or explosive threat is not suspected, but may be a potential terrorist target. The presence of such a monitoring system also serves as a threat deterrent.
In addition to terrorist targets, there is a need to detect, locate and quantify naturally occurring hazardous biological and chemical materials that may be present in the ductwork of the buildings, transportation systems, and infrastructure without having to physically access and search the ductwork. Mold tends to be a significant problem.
Inspection of ductwork, piping, and small areas is difficult to do with people and animals. Many of the piping and duct systems or large sections of piping and ducts are inaccessible and external inspection techniques that require access to the outside wall of the pipe cannot be used. Many of the pipes or ducts are buried underground, or are located beneath the floor of a building or beneath paved areas. Because direct access to the external wall of the pipe or duct is not frequently possible, methods that involve internal inspection of the inside of these systems need to be used.
A common measurement approach for determining whether or not a pipe of duct contains hazardous materials is to use a camera to inspect the inside of the pipe. For short sections of pipe, a small camera is inserted into the pipe on a cable. For example, in U.S. Pat. No. 6,359,645, Sivacoe describes a method of inspecting a pipe, by pushing a video camera through the pipe on a cable. In U.S. Pat. No. 5,939,679, Olsson describes an electromechanical system for inspecting the inside of pipes over distances of several hundred feet for defects and obstructions using a push-cable that mechanically and electrically connects a video camera head to a push reel and video circuit.
A camera and other pipe inspection sensors can be mounted on a robotic vehicle, which is inserted into the pipe and allowed to move down the pipe. For example, in U.S. Pat. No. 6,464,633, Hovis, et al., describes a crawler for inspection of the integrity of 3- to 4-in. diameter piping, where the crawler can carry sensors or a camera to perform the inspection. This approach is acceptable for larger diameter piping, but for small piping, the robotic vehicle may be too large to be used or not be able to move past bends and constrictions in the pipe. The robotic vehicle can be instrumented with a camera, chemical sensors, and sample collectors. Where access to the pipe is possible, the pipe is sometimes cut and analyzed for contamination in the laboratory.
In general, most methods of finding hazardous materials require the insertion of a physical device into the pipe such as a cable or crawler. In addition to cameras and video system, there are a variety of sensors that can detect biological and chemical hazardous materials.
The method of the present invention uses tracers to detect, and/or locate, and/or quantify the threat materials in a pipe or duct, where at least one of the tracers does not interact with the contaminant of interest in the pipe, and one or more tracers that do. Depending on how the measurement is to be done and the requirements on the accuracy and reliability of the measurement, a tracer that does not interact with the target may not be required.
The method described here is very similar to the one described in the patent application submitted by the inventors for characterizing contamination in pipes, ducts, and other fluid flow systems [1], where characterization includes detection, location, and quantification of the contaminant. However, the application objective is very different and the present invention can also use the ducts, pipes, and fluid flow systems as a communication network to apply the method. In addition, the present invention can be used to detect the presence of the hazardous material in a non-fluid flow system such as a room or a container.
Tracers have been used for characterizing subsurface contamination between monitoring wells such as Dense Non-Aqueous Phase Liquids (DNAPLs), Non-Aqueous Phase Liquids (NAPLs), and Light Non-Aqueous Phase Liquids (LNAPL's) such as unleaded gasoline and diesel. Such methods have been used in both the saturated zone using the natural groundwater flow at the tracer carrier fluid or in the vadose zone using an established air flow field as the tracer carrier. In U.S. Pat. No. 6,321,595, Pope, et. al., teaches a method of characterization of organic contaminants in subsurface formations such as nonaqueous phase liquids by injecting partitioning and non-partitioning tracers at one well point and measuring the arrival times of these tracers at another well point. This subsurface tracer approach has also been used to detect releases of a hazardous liquids from underground and above ground storage tanks. This subsurface application has not been used to detect explosives, biohazards, or poisonous chemicals placed in the soil and intended to kill humans. While none of these approaches have been used to identify the presence of these threat materials or any contamination inside a pipe or a duct or a room or a structure, these methods have identified a variety of partitioning tracers that might be used in the method of the present invention.
Advantages. There are a number of important advantages of the method of the present invention over the physical, mechanical, or robotic inspection and measurement systems currently used for detecting, and/or locating, and/or quantifying explosives or biological or chemical substances. The first advantage of the proposed invention is that the same procedure will work on ducts, pipes, conduit, or any fluid flow system of any size and nearly any length. The same method will also work for rooms, compartments, containers, or difficult to access areas associated with buildings, transportation systems, and infrastructure. Tracers are just as easily injected into a small diameter duct, an entire duct system, or a room or a tunnel with and without ductwork.
The second advantage of the proposed invention is that the injected tracers can easily interrogate the entire duct or area within in a building, transportation system, or structure without having to physically place a monitoring device in each duct or area to be interrogated. Gas tracers also inspect the entire surface of the duct or area, including any crevices or nooks that may be difficult to inspect using video approaches. This will result in a more complete and thorough detection capability.
The third advantage of the proposed invention is that it can be used to interrogate an entire building, transportation system, or structure with only a single measurement point.
The fourth advantage of the proposed invention is that there are no moving parts or equipment that has to enter the duct or area to be interrogated. For ducts or areas that may contain explosive vapors or contaminants that could ignite, the interactive tracer technique offers an approach that remains safe. In addition, since no mechanical equipment enters the duct or area to be interrogated, this eliminates the possibility of equipment malfunction or getting “stuck.”
The fifth advantage of the proposed invention is that it can be operated more cost effectively and more safely than other techniques without sacrificing performance. Humans and animals are not placed in harms way for detection or location of the substance of interest.
The sixth advantage is that the proposed invention can also quantify the magnitude of the substances to be detected and located.
The seventh advantage of the proposed invention is that it can be used as a one-time measurement like that provided in a test service or it can be permanently installed in the structure for routine monitoring of the structure.
The eighth advantage is that the same system can monitor or test the health of the building for naturally occurring mold and/or bacteria contamination and can also monitor or test the building for dangerous or hazardous substances placed purposefully to damage the people or the building.